Decorative lamp



FIG. 1 is a front elevational view of the decorative lamp, showing my new design;

FIG. 2 is a left side elevational view thereof, the right side being a mirror image;

FIG. 3 is a top plan view thereof;

FIG. 4 is a bottom plan view thereof; and

FIG. 5 is a rear elevational view thereof. 

The ornamental design for a decorative lamp, substantially as shown and described. 